For a book that was written more than 50 years ago and only discovered in 2011, "Go Set a Watchmen" is rocking the literary world. Originally written as a first draft to the seminal "To Kill a Mockingbird," author Harper Lee has another best-seller on her hands. "Go Set a Watchmen" sold more than 1.1 million copies in the United States and Canada across print, e-book and audio formats in its first week, according to its publisher HarperCollins. It is officially the publisher's fastest selling book ever.

"First week sales of 'Go Set a Watchman' have far exceeded our expectations," Brian Murray, CEO of HarperCollins, said. "We are thrilled to see readers responding to this historic new work from an iconic author like Harper Lee." 

The news does not come as a surprise, as Lee's second book was the most pre-ordered book on Amazon since "Harry Potter and the Deathly Hallows," BBC reported earlier this month. Both of Harper's books are currently two of the top three best selling books on the site.

The release of the "Watchmen" was even celebrated at Barnes & Noble stores with midnight releases, which don't happen as frequently as they used to because of e-readers. It sold more in its first 24 hours at Barnes & Noble than any adult fiction book ever has and, prior to to its release, became the most pre-ordered book at the retailer since Dan Brown's "The Lost Symbol" in 2009, according to The New York Times.

"We're seeing demand across the country for this book," Mary Amicucci, vice president of adult trade and children's books for Barnes & Noble, told The New York Times. "None of us ever expected in our lifetime to have a second book by Harper Lee."

The new book takes place 20 years after the events of "To Kill a Mockingbird." Atticus Finch, a morally straight and quite honorable from "Mockingbird" is a very different person during the civil rights movement in the south, as highlighted in "Watchmen."